pre-exposing / flashing FILM

Discussion in 'B&W: Film, Paper, Chemistry' started by jnanian, Apr 23, 2004.

  1. jnanian

    jnanian Advertiser Advertiser

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    i was talking to someone today - don't want to call him an 'olde timer', but he is much older than me and ... :smile:

    he was telling me all about flashing film before you expose it.
    he suggested that one could pre-flash film - close down about 5 stops, out of focus / neutral gray or overcast north sky - and then expose "normally"

    you will get more details in the negative when you make your actual exposure.

    it doesn't work on every subject, but it will bring out details that would be not captured if the pre-flash was not done.

    i know there are people that have done all sorts of things here, anyone actively do this, or at least tried it?
     
  2. ann

    ann Subscriber

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    yes, with sheet film and a piece of white plexiglass.

    It has been awhile since i have used that technique as i don't do landscape work anymore, it was quite commone for zone work.
     
  3. Bruce Osgood

    Bruce Osgood Membership Council Council

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    I can't find my copy of "the Negative" but Adams spells it out in detail.
     
  4. Jorge

    Jorge Inactive

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    I have used this many times in the past, although I dont seem to use it any longer with the BTZS.

    Anyway, the way I did it was to measure the light through a piece of white plexiglass, I would then put the plexiglass in front of the lens, close 5 stops from the indicated metering and pre exposed the film.

    Works pretty good.
     
  5. Donald Miller

    Donald Miller Member

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    John,

    I have used this and would not hesitate to use it today in high scene brightness ratios.

    I don't stop my lens down five stops, however. What I do is to meter through the opaque acrylic panel and then determine a Zone III placement. I next place the acrylic panel over the camera lens and give the film the first exposure at that Zone III (through the panel) exposure. I then give the film a normal exposure for the second exposure.

    This effects of preflashing film is best illustrated by the following example. If we take the premise that each zone or stop of exposure represents a doubling of light. Then we start out as Zone I having a value of one, Zone II having a value of two, Zone III having a value of four, Zone IV having a value of eight. This continues until we arrive at a number of 128 for Zone VIII.

    By preflashing film in this manner we raise our Zone I exposure to a Zone III 1/3, our Zone II exposure to a Zone III 2/3, our Zone III exposure to a Zone IV, and our Zone IV exposure to IV and one half. The addition of four units of light are miniscule in relation to the 128 units that a Zone VIII would normally have. Additionally this allows us to place our low values at Zone I and compress the brightness ratio by a couple of stops. The compression of values will occur in the shadow regions as opposed to the highlight regions if we were to try to accomplish this at the printing stage by preflashing the paper.
     
  6. jnanian

    jnanian Advertiser Advertiser

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    even though i had never done this, it made sense when i heard it.
    thanks for spelling it all out for me. one of these days i'll have to give it a try.
     
  7. Leon

    Leon Member

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    I use it regularly - made a filter out of a lee gel holder and 2 layers of baking parchment. I do it to ensure that most negs on a roll need roughly the same development time, so i dont have to use N- times for one shot, upsetting the contrasts on all the others. It works really well.
     
  8. gma

    gma Member

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    I am so glad to hear the details of this process. I can certainly use this on high contast Texas subjects. I thought that film flashing was an out of date practice that did not benefit modern films. Actually it is even more important with coated lenses that produce so much contrast. Thanks for the valuable info.
     
  9. glbeas

    glbeas Member

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    I'll have to try this.
    The thread reminds me of an Ebay seller who is unloading a pile of Tri-x film packs and claiming it to be pre-flashed in the ad because of the age of the film. I thought it was a pile of bull and still do, high base fog is just that and I'll bet it's not quite the same as pre flashed film in image quality.
     
  10. Donald Miller

    Donald Miller Member

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    Gary,

    Yes, I agree that this is entirely different. However, one could preflash a holder or two and carry them for those high contrast situations. This could be done, if one wanted, before the actual exposure. Since what we are doing is breaking the film exposure threshold with non image bearing light.

    Obviously for roll film users it wouldn't work the same as sheet film users.
     
  11. ann

    ann Subscriber

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    the old time press guys, did just that. pre-flash some film and carried it around for that special lighting challenge. Of course this was done with the use of speed graflex's.
     
  12. jimgalli

    jimgalli Subscriber

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    This is a card I have in my hand that I hadn't played in years until about 2 weeks ago. I was doing a shot of a banquet group of about 120 optical folks in Las Vegas. All optical experts. No pressure at all. I had the Nikon digital (hell, I'm not crazy) and the 7X17 Folmer & Schwing set up. When I measured my spread in the AM sun for the B&W pic it was like 5 stops from zone 3 shadow to where the people in sunlight would be. I carry an old Polaroid flash diffuser with me just in case I need it. Took a reading through the diffuser with the spot meter and then put it over the lens and exposed through it for Z 1 1/2 a few minutes before the group arrived. Then when my group was in place I exposed as normal. As a result I got a great neg with excellent shadow detail and nice highlights also. Wish I had the Polaroid number of that piece, but here is a picture of one on an old 195 flash.

    http://tonopahpictures.0catch.com/c6_1.jpg

    Jorge, how do you include html in these posts?
     
  13. Ed Sukach

    Ed Sukach Member

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    I've been reading this thread with interest.
    For me, pre-flashing *film* is not a viable option: it would mean re-rolling 120 - something I have never been able to do.

    I *do* pre-flash paper - especially color paper. It is a "very" effective way to control and modify excessive contrast.

    More and more, I'm gravitating toward "pure" negatives. I have softeners and all sorts of pre-lens filter, and the only ones I use are a few - very few - black and white; orange, green and, of course Red #25 (always with IR) and then on a very limited basis.

    Where I do "soften" is in the enlarger. I have found in printing, that a "softener" over the enlarging lens can effectively reduce apparent "grain" (every once in a while I'll go through a Keystone Kops routine trying to use the grain focuser with a softening filter in place - there just isn't any "grain" to focus upon).

    My favorite developer is Rodinal - and it is a "clean" developer - its action is not to increase grain size - but to present it with extreme efficiency. There is no 'smearing' of grain boundaries- the *big* secret of so-called "fine grain" developers. Everyone agrees to this: Excellent tonality - at the price of "baseball-sized" grain ... but ... I can make the "grain" go away with enlarger filtration.
     
  14. Leon

    Leon Member

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    Ed - not sure what you mean? Do you mean pre-flashing the whole roll? I use roll film and only pre-flash the frame I'm using through a double exposure (1. flash, 2. image), some images will be pre-flashed on the roll, others wont be. Have i missed your point?

    cheers

    Leon
     
  15. jnanian

    jnanian Advertiser Advertiser

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    jim:

    the diffusion device looks similar to what i have for my lumedyne - i think it is called " the tupperware lid" :smile:

    ed: i know the person i spoke with ( also ed :smile: ) spoke about pre-exposing on frame by frame basis - by double-exposing and shifting where "zones of detail" would be. he used to do it with both color chrome film and b&w film. i know what you mean about re-rolling film. i used to use a yashica-mat double and did a bunch of double-exposed images. no re-wind button, and it *was* a royal pain in the neck to re-roll. nothing ever alligned the way i wanted. :sad:


    this is great! its good to know this technique is still alive and well, and when i eventually try "pre-flash" work, i can ask for some useful advice from people who do it :smile:

    (i wish i had known about this before when i had lighting-conditons-from-hell to deal with.)
     
  16. Ed Sukach

    Ed Sukach Member

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    I *had* envisioned this as a "whole roll" exercise. Frame by frame would be awkward with the Hasselblad, having to work around the double exposure prevention, - I'd have to expose, and not rewind; replace the darkslide, remove the magazine, rewind and replace the magazine and re-expose. Awkward, but possible.

    I'd much rather capture as much information as possible on the film, and manipulate it afterwards in the enlarger .. that would keep my options open.

    Color film, especially. has the ability to capture a wide range of values ... I would estimate from 8 to 12 "stops". Color paper, generally, cannot handle that much, - so preflashing becomes a viable tool.
     
  17. Leon

    Leon Member

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    is there really no option for a double exposure on a HAssleblad? I'm amazed - the mighty beast perhaps isnt quite as mighty as I first thought :wink:
     
  18. jnanian

    jnanian Advertiser Advertiser

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    i assisted a fashion/portrait/annual report guy in the 80s - he had a hasselblad --- i used to double expose everything for him. needlesstosay, i don't think his 'blad's double exposure preventure was up to snuff :smile:

    ed, i can show you how it is done! :wink:
     
  19. Seele

    Seele Member

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    In Popular Photography, June 1976, there's an article by Bob Schwalberg on an invention by Melrose R. Cole, of MA, which he called CPA (Concurrent Photon Amplification) and took six years to develop. It requires a camera with focal plane shutter to be modified to have a number of small light bulbs put into the dark chamber, which gives a correct dose of uniform non-image light on the film. At the time Cole charged $750 for the conversion.

    The Photography How-To Guide, summer 1978, also has an article by Gerry Kopelow, not only as a follow-up, but also details the method of constructing your own, using components available off-the-shelf at the time.

    The original Cole design used filament lamps which have to take moment to warm up to the correct output level, so a mechanical arrangement was made to fit over the shutter release button; you press it down to activate the bulbs, and further pressure hits the shutter release. The Kopelow version employed LEDs which give instantaneous response.

    With the availability of smaller and more power-efficient parts, I feel that an updated design can make a lot of sense, now, who is ready to rise to the challenge?